1. Field of the Invention
The present invention relates to porous particles of a calcium phosphate compound and a process for their production. The porous calcium phosphate particles according to the present invention are particularly useful as packings for liquid chromatography and also as fine ceramic materials in other technical fields.
2. Description of the Related Art
As is well-known, calcium phosphate compounds are utilized in various technical fields. For example, because they exhibit excellent biocompatibility, calcium phosphate compounds can be utilized as a biological material. In addition, they can be utilized as packings for liquid chromatography because of their good selective adsorptivity to proteins and similar substances.
Japanese Unexamined Patent Publication (Kokai) No. 62-91410 teaches a process for the production of granules of hexagonal crystals having a certain unit lattice constant for chromatography, which comprises the steps of granulating gels of hydroxyapatite and firing the resulting granulates at a temperature of 400.degree. to 700.degree. C. However, because the obtained granules of hexagonal crystals of hydroxyapatite have an insufficient strength due to the use of a firing temperature of 700.degree. C. or less, they are not suitable as a packings for chromatography, especially for high performance liquid chromatography (HPLC). To enable the use of hydroxyapatite granules for HPLC packings, it is therefore desired to improve the properties such granules.
On the other hand, in the field of fine ceramics, it is desired to provide finely divided particles of the ceramics material having high strength. The highest fineness of the particles should be given.